The present invention relates to a device for controlling variable-pitch blades in a turbomachine such as an aircraft turbojet or turboprop.
A turbomachine of this type comprises one or a plurality of variable-pitch guide blade stages which are mounted between the wheels of a compressor. These variable-pitch blades are carried by the turbomachine stator and are adjustable in position about the axes thereof to optimise gas flow in the turbomachine engine.
Each variable-pitch blade comprises a cylindrical pivot at each of the ends thereof, said pivots defining the axis of rotation of the blade. The radially external pivot is engaged in a cylindrical duct of an external annular casing of the turbomachine and is connected by a connecting rod to a ring which is mounted about the casing and is in turn connected by a lever to a control shaft actuated by a cylinder. The control shaft runs parallel to the casing axis and may be connected to one or a plurality of the abovementioned rings to control one or a plurality of guide blade stages.
The cylinder rod is connected to the control shaft by a radial arm rigidly connected to the control shaft. The linear movement of the cylinder rod causes the control shaft to rotate about the axis thereof and the or each ring to be driven in rotation about the casing. The rotation of a drive ring is transferred by the corresponding connecting rods to the external pivots of the blades of one stage and rotates same about the axes thereof.